Bagworms identification and plants to check

Asked July 20, 2018, 3:23 PM EDT

I have seen the response to the question regarding treatment but I am wondering if there is a fact sheet or other resource you recommend to learn how to IID bagworms and what trees and shrubs to check. It would be nice if all: ID, plants and treatment were on one source. Thanks for your help

Information on insect pests should be investigated first at cooperative extension offices, or university based websites. These internet locations most often have the up-to-date options available from a more unbiased viewpoint. At the end of this response is a list of other sites for bagworm management. The site provided in other response is also a good location for information; however not all garden centers, botanical gardens, etc. are as well informed.

Bagworms are fairly simple to identify and they have a variety of host plants they commonly attack. Arborvitae, Leyland cypress, pines, firs and junipers are among the most common hosts. They emerge around the end of May through late June and produce silk which they release into the air. This is called ballooning, and local breezes may catch the silk which carries the young bagworm (caterpillar) to a new location/different plant. The caterpillar begins to feed, and immediately begins to incorporate some of the host plant around itself in the form of a bag. The head and first pair of legs are usually the only parts of the caterpillar exposed as it feeds because the rest is surround by the bag it makes. The bag is relatively small and light early in the life of the caterpillar; thus, the caterpillar carries it upright. This is called the dunce-cap stage and is the stage most susceptible to Bacillus thuringensis. The remainder of the summer the caterpillar feeds and incorporates food particles into a bag that continues to increase in size as the caterpillar grows. Successful control of bagworms is obtained by treating the foliage of the plant, and not by spraying the bag directly. Mid-August the caterpillars are starting to pupate (make a chrysalis) and spraying hosts is much less effective. In September, the bagworms are either becoming moths or are mature insects that remain within the bags. Females call males to them with pheromones and mating occurs during the fall (September onwards). Females lay eggs then die, and the eggs remain in the bag protected from the environment until the following May when they hatch.

There are a couple of bagworm species in our area, and most of them prefer feeding on evergreens or coniferous plants; however there are some you can see feeding on maples or oaks among other trees.